Automated door assembly and methods, press used therewith, and adhesive therefor

ABSTRACT

A door pressing system for pressing interior passage doors, exterior entry doors, bi-fold doors, and/or closet doors features a multi-door pressing station including first and second presses, a loading device, and a discharging device. The pressing station is configured to alternatively move the first and second presses into operative alignment with the loading and discharging devices. The press in operative alignment delivers a pressed assembled door to the discharging device and receives an assembled door layup to be pressed from the loading device. The other press that is out of operatively alignment presses an assembled door received therein. Additional methods and systems are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application claims the benefit of priority to U.S. provisionalapplication No. 61/793,524, filed Mar. 15, 2013, the complete disclosureof which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed to systems and methods, particularlyautomated systems and methods, for manufacturing doors having first andsecond door facings and internal door frames, multi-door pressingstations for use therewith, and adhesives and doors processed andmanufactured in the course of using the systems and practicing themethods.

BACKGROUND

A door such as a hollow core door typically includes two molded or flushdoor skins (sometimes called “door facings”) attached to opposite sidesof an interior door frame, which is typically made of wood but sometimesmetal or composites. The door facings are often molded from a compositeof wood fiber and resin compound, although fiberglass-reinforcedpolymeric door facings and steel door facings are also known. The doorframe typically includes stiles and rails positioned around theperimeter of the door that together form the frame. The interior of thedoor may optionally include a core.

Manual assembly of doors is relatively labor intensive, expensive, andsubject to quality variations. During manual assembly, a door facing isplaced on a production table with its intended exterior surface facedown. Adhesive is applied, typically via a roll coater, to the oppositesides of the stiles and rails. The core and/or lock block(s), if any,are likewise coated. The adhesively coated frame parts (stiles andrails) are then placed by hand on the door facing on the table.Typically, the rails are placed at the top and bottom of the doorfacing, and the stiles are placed on opposite sides of the door facing.With the adhesive applied to a second upward-facing side of the stilesand rails, a second door facing is placed with its interior surface onthe second side of the frame. Another door facing is then placed withits exterior surface face down on the previously assembled door and theprocess repeated until a stack of doors has been assembled. In thismanual assembly process, the assembled doors should be handledcarefully, given that the components of the door are in a loose “layup”state and can easily shift during transportation.

In the above-described manner, each successive door assembly is stackedon top of the previous door assembly until a predetermined quantity ofdoor assemblies has been stacked. The stack of door assemblies is thentransported to and loaded in a press. The press applies pressure to theentire stack for a period of time sufficient to allow the adhesive tobond the door facings to their respective frames. Conventionaladhesives, such as polyvinyl acetate, may take approximately thirtyminutes or more to cure or harden in the press before the door reaches“green” strength. The door achieves “green” strength when the adhesivehas reached sufficient bonding strength to hold the door componentstogether for further handling.

Once green strength is achieved, the doors may be removed from the pressand moved to an in-process inventory until the adhesive reaches adequatecure strength. Depending upon the adhesive used and ambient conditions,the doors may need to remain in inventory for a relatively long periodof time, for example two hours or more, or even as long as twenty-fourhours, before the adhesive reaches adequate bonding strength for finalprocessing.

After reaching adequate cure strength the doors are then moved to afinal processing station. Final processing includes edge trimming thedoors to customer specification and optional coating and/or painting ofdoor skins and exposed edges of the stiles and rails around each doorperimeter. Using this process, manufacturing time for a door may betwenty-four hours or more, from the time production is initiated to theresulting finished door is complete and ready for delivery to a customeror user.

SUMMARY

According to an embodiment of the invention described in greater detailbelow, a door pressing system is provided for pressing doors, such asinterior passage doors, exterior entry doors, bi-fold doors, and/orcloset doors. In accordance with this embodiment, the system includes amulti-door pressing station featuring a first press including a firstset of platens, and a second press including a second set of platens,each set of platens respectively having at least one platen movablerelative to the other platen of the set of platens between an open stateand a closed state. The system further includes a loading materialhandling and movement device configured to deliver assembled doors in alayup state to the multi-door pressing station, and a dischargingmaterial handling and movement device configured to receive assembleddoors that have been pressed by the multi-door pressing station. Themulti-door pressing station is configured to alternatingly move thefirst and second presses between a loading/unloading position and apressing position. In the loading/unloading position, one (e.g., thefirst) of the first and second presses is in the open state andoperative alignment with the loading and discharging material handlingand movement devices to receive at least a first of the assembled doorsin the layup state delivered by the loading material handling andmovement device and to discharge at least a second of the assembleddoors that has been pressed to the discharging material handling andmovement device. In the pressing position, the other (e.g., the second)of the first and second presses is in the closed state for pressing athird of the assembled doors and is out of operative alignment with theloading and discharging material handling and movement devices. In onevariation of this embodiment, the multi-door pressing station is movablevertically between the loading/unloading position and the pressingposition. In another variation of this embodiment, the first and secondpresses move alternatingly between the loading/unloading position andthe pressing position.

In accordance with another embodiment, a system for making any ofpassage doors, interior passage doors, exterior entry doors, bi-folddoors and/or closet doors includes at least one framing station, atleast one adhesive coating station, at least one assembly station, andat least one pressing station. The framing station is configured toreceive framing components such as rails and stiles, and optionally lockblocks and/or cores, from delivery component lines, especially automateddelivery component lines, to assemble door frames. The assembled doorframes are sent to an adhesive coating station which applies adhesive tothe door frames. The assembly station optionally orients the door skinsand joins first and second door skins to opposite surfaces of the framesto form assembled doors. The pressing station includes a first press anda second press for alternatingly pressing the assembled doors andreceiving/discharging the assembled doors prior to/after pressing. Afterthe assembled doors are discharged from the pressing station, thepressed assembled doors may be received by a non-linear accumulator.

In accordance with a further embodiment, a system is provided for makingdoor frames for at least one of interior passage doors, exterior entrydoors, passage doors, closet doors, and/or bi-fold doors. The systemincludes a core attachment station for connecting an expandable core toa top rail and a bottom rail, and a robotic system, including a pair ofgrippers, for respectively gripping top and bottom rails. The grippersdraw the top and bottom rails apart to expand the attached expandablecore, and the robotic system delivers the spaced apart top and bottomrails and the expanded core to a framing station where the top andbottom rails are attached to a pair of stiles to form a door frame. Theframing station may include a jig system for supporting and holding therails and stiles at the four corners of the door frame where the railsand stiles abut during the attachment process. The stiles and rails maybe attached via quick-setting adhesive, a mechanical fastener or acombination thereof to allow the frame to be self-supporting.

In accordance with a further embodiment, a system is provided for makingdoor frames for at least one of interior passage doors, exterior entrydoors, passage doors, closet doors, and/or bi-fold doors. The systemincludes a framing station including a jig system for supporting andholding the rails and stiles in the arrangement of a door frame. One ormore lock blocks may be secured to the door frame components, typicallya stile, prior to the attachment process at the jig station. Adhesive isapplied and/or mechanical fasteners are employed to join the rails,stiles, and another other frame components so as to allow the frame tobe self-supporting. In accordance with this embodiment, a lock blockselected from a set of lock blocks may be adhered to a respective stileprior to being delivered to the framing station. Likewise, an expandablecore selected from a set of expandable cores may have its opposite endsadhered to respective pairs of rails prior to being delivered to theframing station.

In accordance with a variation of the above and other embodiments, thejig system includes four clamping members, one at each of the fourcorners where the rails and stiles abut.

According to another variation of the above and other embodiments, eachof the clamping members further includes at least one adhesive nozzlefor applying adhesive to associated edges of the stiles and/or railswhere the rails and stiles abut.

In accordance with a further embodiment, a door pressing system formaking doors, in particular at least one of interior passage doors,exterior entry doors, bi-fold doors, and/or closet doors is provided.The system includes a multi-door pressing station, which in turnincludes at least a first press and a second press, each having apair/set of movable platens, for receiving assembled doors. The pressingstation is adapted so that one of the presses performs a pressingoperation on at least one assembled door layup while the other pressreceives and/or discharges a pressed second assembled door. A loadingsystem is provided for successively delivering door layups to thepressing station, and a discharging system is downstream of the pressingstation for carrying off pressed assembled doors. The pressing stationis operable to selectively and alternatingly move the first and secondpresses between a first (loading/unloading) position wherein one of thepresses is oriented to receive at least a first assembled door layupfrom the loading system and discharge at least a pressed secondassembled door to the discharge system, and a second (pressing) positionin which the other of the presses is oriented to press at least a thirdassembled door.

In accordance with a variation of the above and other embodimentsdisclosed herein, presses of the multi-door pressing station are movablein tandem with one another between the first and second positions.Movement may be accomplished using suitable hydraulic equipment, forexample. The movement may be vertical movement between upper and lowerpositions with correspond to the first and second pressing positions, orvice versa.

In accordance with a further embodiment, a door assembly system isprovided for pressing and curing a plurality of assembled doorsincluding door skins adhered to a frame assembly. The door assemblystation features a multi-door pressing station including at least firstand second presses, each press having a pair of movable platens, formoving the platens between and open state for receiving door assembliesand a closed state for pressing door assemblies. The pressing stationapplies pressure to each assembled door in the first press to perform apressing operation on the assembled door(s) in the first press whilereceiving and/or discharging one or more assembled doors into/from thesecond press. A non-linear accumulator is downstream of the pressingstation for holding at least first and second pressed assembled doorsduring an adhesive curing process.

In accordance with a further embodiment, the multi-door pressing stationdelivers pressed assembled doors to an accumulator in the form of a starconveyor that rotates a plurality of pressed assembled doors through acircular path. The accumulator holds the pressed assembled doors duringa curing process.

In accordance with still a further embodiment, a system is provided formaking door frames for at least one of interior passage doors, exteriorentry doors, passage doors, bi-fold doors, and/or closet doors. Thesystem includes a core attachment station for attaching an expandablecore to a top rail and a bottom rail with a first adhesive. A lock blockattachment station connects at least one lock block to a stile with asecond adhesive, which may be the same as or different than the firstadhesive. A robotic system delivers the top and bottom rails and theadhesively attached core to a framing station where the top and bottomrails are adhesively attached to a pair of stiles to form a door frame.

Still another embodiment disclosed herein features a method ofassembling a door, which features: successively delivering assembleddoors in a layup state via a loading material handling and movementdevice to a multi-door pressing station including first and secondpresses; discharging at least a first of the assembled doors having beenpressed from the first press of the multi-door pressing station to adischarging material handling and movement device, and loading at leasta second of the assembled doors in the layup state into the first pressof the multi-door pressing station while the first press is in operativealignment with the loading and discharging material handling andmovement devices, and simultaneously pressing at least a third of theassembled doors in the second press of the multi-door pressing station;moving the second press into operative alignment with the loading anddischarging material handling and movement devices; and discharging theat least third of the assembled doors having been pressed from thesecond press and loading at least a fourth of the assembled doors in thelayup state into the second press while the second press is in operativealignment with the loading and discharging material handling andmovement devices, and simultaneously pressing the at least second of theassembled doors in the first press. The embodiment may further includeapplying adhesive to door frame components and frame the door framecomponents and applied adhesive into door frames; and securing first andsecond door skins on opposite surfaces of the door frames to provide theassembled doors in the layup state.

Still another embodiment of the present invention features an assembleddoor or pre-assembled door, which may include one or more of thefollowing features: a door frame with abutting ends and edges of thestiles and rails adhesively attached to one another; an expandable orexpanded core adhesively and/or mechanically attached to rails; lockblocks adhered and/or fastened to a stile prior to the stile beinglaid-up as a door frame or door assembly, and other structures describedherein.

Other embodiments, including apparatus, systems, stations, methods,doors, door skins, and the like which constitute part of the invention,will become more apparent upon reading the following detaileddescription of the exemplary embodiments and viewing the drawings. It isto be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andtherefore not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated in and constitute a part ofthe specification. The drawings, together with the general descriptiongiven above and the detailed description of the exemplary embodimentsand methods given below, serve to explain the principles of theinvention. In such drawings:

FIGS. 1A, 1B, and 1C are partial schematic views collectivelyillustrating an exemplary automated door production line, wherein FIG.1C illustrates finishing components downstream of the pressing station;

FIG. 2 is a schematic view of a frame assembly station of the doorproduction line according to the present invention.

FIG. 2A is an enlarged partial view of the frame assembly station ofFIG. 2, depicting the rails and core after being assembled at the coreattachment station where the core is adhered to a pair of rails;

FIG. 2B is an enlarged partial view of the frame assembly station ofFIG. 2, depicting the rail grippers moving apart the rails to therebyexpand the attached core as the distance between the rails is made tomatch a length of an associated stile;

FIG. 2C is an enlarged partial view of the frame assembly station ofFIG. 2, depicting the rail grippers delivering the rails and core to aframe assembly jig;

FIG. 2D is an enlarged partial view of the frame assembly station ofFIG. 2, depicting a stile, which includes an associated lock blockaffixed thereto, being delivered by arms to the frame assembly section;

FIG. 2E is an enlarged partial view of the frame assembly station ofFIG. 2, depicting the frame assembly jig from an angle different thanthe angle shown in FIGS. 2C and 2D wherein an assembled frame is shownwith another rail/core assembly being suspended above the alreadyassembled frame;

FIG. 2F is an enlarged partial view of the frame assembly station ofFIG. 2, depicting the frame assembly jig assembling a frame while analready assembled frame is transported by conveyor from the jig towardthe adhesive coating station;

FIG. 3 is a schematic of the frame assembly jig according to the presentinvention with an assembled frame being suspended by four clamps whilerail grippers expand a rail/core assembly above the frame conveyor;

FIGS. 4A-4C are partial views depicting the frame handling arms whichretrieve the door frame from the adhesion station and place the doorframe onto the bottom door skin at the bottom skin layup station;

FIG. 4D is a schematic showing the frame handling arm used inconjunction with an alignment mechanism for squaring the door frameduring the layup process;

FIGS. 5A-5C are partial views depicting a top skin layup station and apick-and-place mechanism that utilizes suction cups to lift and place atop skin onto an assembled frame at a top skin layup station;

FIGS. 6A-6E are partial views respectively depicting the verticallymovable two-press pressing station at various stages of operation;

FIGS. 6F and 6G are schematic illustrations depicting the two presses intheir respective loading positions;

FIG. 7 depicts a pair of non-linear accumulators in the form of starconveyors; and

FIG. 8 depicts an exemplary motor-driven star conveyor.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S) AND EXEMPLARY METHOD(S)

Reference will now be made in detail to exemplary embodiments andmethods as illustrated in the accompanying drawings, in which likereference characters designate like or corresponding parts throughoutthe drawings. It should be noted, however, that the invention in itsbroader aspects is not limited to the specific details, representativedevices and methods, and illustrative examples shown and described inconnection with the exemplary embodiments and methods.

FIGS. 1A-1C collectively depict an automated door production lineaccording to an embodiment of the present invention.

In an exemplary embodiment, the door production line is a synchronoussystem designed to operate at a specific rate of door build, for exampleone door produced per unit of time. In order to avoid bottlenecks andmaximize throughput, each step in the process, including transportation,occurs at a preset rate intended to assure that the door build rate isachieved and optionally optimized. Therefore, it is important to providesuitable press time and proper adhesives and adhesive application tosufficiently bond the components of the door together. Improper bondingcan lead to quality issues, or failure of the frame which would thusnecessitate suspension of line operation.

The production line may be divided for purposes of discussion into five(5) different sections or stages of the production process. First,referring to FIGS. 1A and 2, at least one frame assembly station 100 isprovided whereby rails 110, stiles 120, lock blocks 130 and cores 140are delivered to a central framing jig 101. At the central framing jig101, the frame components are assembled into a door frame 150. In FIG.1A, a second frame assembly station 100′ is also shown. Thereafter, asbest shown in FIG. 1B, at least one adhesive coating and layup station200 receives assembled frames 150 and the assembled frames 150 arecoated with adhesive at coater 210, after which door skins 220, 230 areapplied to the assembled door frame 150. The door skins 220, 230 aredelivered from a door skin delivery station 300. As further shown inFIG. 1B, the assembled doors or door layups are then passed to apressing station 400 and thereafter to an accumulator station 500. Theassembled and pressed doors are thereafter passed to a single conveyor600 where the doors are delivered to finishing stations where theassemble doors may be trimmed, painted, inspected, and stacked.

With reference to FIGS. 1A and 2, the frame assembly station 100receives rails 110, stiles 120, lock blocks 130, and cores 140, whichare delivered to the central framing jig 101 by material handlingdevices, which preferably are moving conveyors, such as conveyors havingcontinuous moving belts for delivery of the frame components. The rails110, stiles 120, lock blocks 130, and cores 140 preferably are deliveredin sets of predetermined numbers and arranged in a form that facilitatesmaintenance of the door build rate. Various material handling andmovement devices and methods may be used to transport components of eachdoor assembly, and are simply designated by the arrows in the individualstations and between stations. Material handling and movement devicesmay include, for example, conveyors, gantries, manipulators, grippers,automated guided vehicles, pick and place systems and automatedstorage/retrieval systems. The components and stations of the productionline may be operated by an operator's control, automatically byutilizing various sensors including optical, magnetic, and radiosensors, or any combination of manual and automatic operation. Thoughspecific examples of material handling and movement are provided in theexemplary description of certain stations, these may be modified aswould be understood by one of ordinary skill in the art upon viewingthis disclosure.

Core attachment station 142, best shown in FIG. 2, includes an automatedrail delivery system whereby rails 110 are introduced by an automatedrail picking and placing device, such as a mechanical arm, which removesthe rails 110 from the delivery device, such as fork truck 10. Theautomated rail picking and placing device places a predetermined numberof rails 110 onto a moving conveyor belt that delivers the rails 110 toa rail indexing device 112 that selects a pair of rails 110 a, 110 bfrom the rail delivery system. In an exemplary embodiment the raildelivery system includes a top rail conveyor and a bottom rail conveyor,although a single rail conveyor or more than two rail conveyors may beused as discussed in connection with the first and second stileconveyors. As also shown in FIG. 2, a single top rail 110 a may beselected from the top rail conveyor and a single bottom rail 110 b isselected from the bottom rail conveyor. In various exemplaryembodiments, a door having more than one top rail 110 a, such as adouble top rail (not shown), more than one bottom rail 110 b, such as adouble bottom rail (not shown), or both a double bottom rail and doubletop rail, and/or one or more intermediate rails (not shown) may bedesired. Therefore, the rail indexing device 112 is capable of variablyselecting a single rail 110 a, 110 b or multiple rails from the top railconveyors, the bottom rail conveyors, and optionally intermediate railconveyors (not shown). If more than a single top and/or bottom rail 110a, 110 b is selected, the two or more top rails 110 a are attached, forexample, by fasteners or an adhesive such as a hot melt adhesive to forma multi (e.g. double) top rail. Two or more bottom rails 110 b may beprocessed in similar manner to form a multi (e.g., double) bottom rail.

After being selected, the rails 110 a, 110 b are moved to a coreattachment station 142. At the core attachment station 142, a core 140is connected to the top rail 110 a and to the bottom rail 110 b, forexample, by a hot melt adhesive. Additionally or as an alternative,fasteners may be used to establish or strength the connection. The core140 is preferably placed onto a material delivery mechanism by anoperator O1 and then is brought to the core attachment station 142 by aconveyor or indexing device 144. The core 140 may be an expandable core,such as made from expandable cardboard, honeycomb, or any suitablesubstance depending on the door that is to be assembled. In an exemplaryembodiment, the core 140 is an expandable corrugated cardboard core orhoneycomb paper core. The production line is set up and operated so thatthe core 140 is variable and optionally different cores 140 may beselectively attached to the rails or omitted from the assembled frame.Optionally, the core may be formed in situ.

A thermoplastic hot melt adhesive attaches the core to the rails 110 a,110 b. The thermoplastic hot melt adhesive may be preheated and appliedin a liquid, softened, or molten state. For example, the liquid adhesivemay be extruded from nozzles under pressure. The adhesive bonds nearlyinstantaneously so that the rails may be moved apart in order to allowthe core to be expanded quickly after contacting the rails and adheringthe core and rails to one another. The bond strength is sufficient toallow the core to remain attached to the rails as the rails are movedapart from one another and also to remain attached and fixed as therails are assembled into a frame and the assembled frame is connected todoor skins.

As best shown in FIG. 2, a stile assembly station includes an automatedstile delivery system through which stiles 120 are introduced by anautomated stile picking and placing device, such as a mechanical arm,which removes the stiles 120 from the delivery device, which isillustrated as a fork truck 20. The automatic stile picking and placingdevice places a predetermined number of stiles 120 onto two conveyorbelts 122, 124 that deliver the stiles 120 to respective stile indexingdevices 126, 128. Stile indexing devices 126, 128 deliver one set ofstiles 120 to the left side of the frame assembly jig 101 and anotherset of stiles 120 to the right side of the frame assembly jig 101. Inthe preferred embodiment, the stiles 120 delivered from the conveyor 122are passed to the stile indexing device 126 for delivery to the rightside of the frame assembly jig 101, and the stiles 120 delivered fromthe conveyor 124 pass below the frame assembly jig 101 to the stileindexing device 128 on the left side of the frame assembly jig 101.

The stile assembly station includes an automated lock block deliverysystem whereby lock blocks 130 are introduced by an automated lock blockpicking and placing device, such as a mechanical arm, which retrievesthe lock blocks 130 from a carrier device, which is illustrated asanother fork lift 30 in FIG. 2. The automated lock block picking andplacing device selectively places lock blocks 130 for delivery to twoconveyor belts 132, 134 that deliver the lock blocks 130 to respectivelock block indexing devices 136, 138 in the form of rollers whichdeliver the lock blocks 130 one-by-one to the left side of the frameassembly jig 101 and one-by-one to the right side of the frame assemblyjig 101.

Both the stiles 120 and the lock blocks 130 are moved to lock blockattachment stations 139 a, 139 b. At the lock block attachment stations139 a, 139 b, the lock blocks 130 receive adhesive from a pressurizednozzle and are positioned in front of a respective stile 120 in order tobe affixed to the associated stile 120. Each stile 120 moves in thedirection of the arrows depicted at the stile indexing devices 126, 128.In the preferred embodiment, the lock blocks 130 are attached to thestiles 120 via adhesive, for example a hot melt adhesive, but the lockblocks may be attached by a mechanical fastener, or a combination ofadhesive and mechanical fastener. While FIG. 2 depicts a single lockblock 130 being attached to each stile 120 on the right and left sidesof the frame assembly jig 101 at the lock block attachment stations 139a, 139 b, optionally only a single lock block 130 may be attached at oneof the lock block attachment stations 139 a, 139 b. Optionally, multiplelock blocks may be attached to the stiles 120 at the stations 139 a, 139b. The movement and handling of all the components in frame assemblystation 100 may be handled manually or automatically by robotic systemssuch as pick and place robotic arms, robotic indexers, and the like. Inthe illustrated embodiment, the rails 110, the stiles 120, and the lockblocks 130 are handled automatically.

Each lock block 130 is secured to its associated stile 120 preferablythrough use of a thermoplastic hot melt adhesive, fastener, orcombination thereof. The adhesive is preferably a viscous, fast settingadhesive that is applied to either the lock block 130 and/or the stile120 at a point in the production line that allows the lock block 130 tobe brought into engagement with the stile 120 before the adhesive hasset. The bond strength is such that the lock block remains secured tothe stile 120 during the frame assembly process. The assembled frame isthereafter transferred onto the associated door skin and thereafter theassembled door layup is transported to the press 420, as described ingreater detail below.

As discussed in more detail below, the central framing section includesa frame assembly jig 101 for supporting and holding the rails 110 andstiles 120 by raised arms until four clamps 180 a, 180 b, 180 c and 180d grasp the frame at the corresponding four corners where the rails 110and stiles 120 abut during the attachment process to allow the frame 150to be self-supporting. Thereafter, the assembled frame 150 is passed toa conveyor for delivery to the adhesive coating station while anotherdoor frame 150 is assembled on the frame assembly jig 101.

FIGS. 2A-2F collectively illustrate a frame assembly process performedat the frame assembly jig 101. FIG. 2B illustrates the rails 110 a, 110b and the core 140 after being assembled at the core attachment station142 where the core 140 is adhesively adhered between and to a pair ofrails 110 a, 110 b. A pair of rail grippers 162, 164 grasps the rails110 a, 110 b and deliver the rail/core assembly to the frame assemblyjig 101. As best shown in FIG. 2B, the rail grippers 162, 164 areconfigured to increase the distance between rails 110 a, 110 b tothereby expand the core 140 as the distance between the rails 110 a, 110b is made to match a length of an associated stile 120.

FIG. 2C depicts the rail grippers 162, 164 delivering the rails 110 a,110 b and the core 140 to the frame assembly jig 101. As best shown inFIG. 2D, an assembled frame 150 is shown on the lower conveyor 155.FIGS. 2C and 2D are additional views illustrating the assembled frame150 on the lower conveyor 155 while the rail grippers 162, 164 reach theframe assembly jig 101. FIG. 2D also illustrates a stile 120 a, whichincludes an associated lock block 130 a affixed thereto, being deliveredby arms 101 a to frame assembly section.

FIG. 2E depicts the frame assembly jig from a different angle than theangle shown in FIGS. 2C and 2D. In FIG. 2E, an assembled frame 150 a isshown with another rail/core assembly 143 suspended above the previouslyassembled frame 150 a. The assembled frame 150 a is held in place byfour clamps 180 a, 180 b, 180 c and 180 d (FIG. 2) positioned at thefour corners of frame 150 a while the rail grippers 162, 164 (FIG. 2C)deliver the next rail/core assembly 143 to the frame assembly jig 101.Also shown in FIG. 2E is another pair of stiles 120 with associated lockblocks 130 on opposite sides of the rail/core assembly 143. Theadditional stiles 120 are delivered by arms 101 a to the frame assemblyjig 101 for adhesion to the rail/core assembly 143 while the four clamps180 a, 180 b, 180 c and 180 d release the assembled frame 150 a onto theconveyor 155.

In the preferred embodiment, there are three arms 101 a on each side ofthe frame assembly jig 101 and each arm 101 a is provided with conveyorbelts 101 b that are driven by motorized rollers 101 c mounted at theend of each arm 101 a. The conveyor belts 101 b convey the stiles 120 tothe frame assembly jig 101. Once the four clamps 180 a-180 d grasp theassembled frame 150, the arms 101 a retract to permit the assembledframe 150 to interact with and be transported by the conveyor 155disposed below the jig 101.

As best seen in FIG. 2E, the core 140 dangles or bows downwardly due toits weight because it is held in place only by way of its adhesion tothe rails 110 that are suspended by the rail grippers 162, 164. The core140 is expanded cardboard or like paper-like material and thus haslittle structural strength when so suspended.

FIG. 2F depicts the frame assembly jig 101 assembling a frame while theimmediately previously assembled frame 150 is transported by theconveyor 155 from the jig 101 to the adhesive coating station describedbelow.

As described above, the assembly of the attached lock block 130 and thestile 120 and the assembly of the attached rails 110 a, 110 b and core140 are transferred to the frame assembly area and supported by frameassembly jig 101. Robotic handling devices such as a clamp and gantrysystem may be used to deliver the frame components to the frame assemblyjig 101. After the expandable core 140 is adhered to the rails, therails 110 a, 110 b are drawn apart to expand the core 140. The rails 110a, 110 b and stiles 120 are then secured together to form the assembledframe 150. The rails 110 a, 110 b and stiles 120 may be attached to oneanother using mechanical fasteners, adhesive, for example, a hot meltadhesive, or any combination of fasteners and adhesive. In variousexemplary embodiments, different combinations of the lock blocks, thestiles, the rails, and the core may be delivered to the production line.It should be noted that the term frame 150 used throughout the rest ofthis description includes the assembled stiles 120, rails 110, optionallock block(s) 130, and optional core(s) 140.

FIG. 3 is a schematic of the frame assembly jig 101 according to thepresent invention with an assembled frame 150 suspended by four clamps180 a, 180 b, 180 c and 180 d while rail grippers 162, 164 expand arail/core assembly above the frame conveyor 155. As best shown in FIG.3, the arms 101 a of the frame assembly jig 101 deliver stiles 120 fromopposite sides of the jig 101. The arms 101 a include conveyor belts 101b driven by motorized rollers 101 c at the terminal ends of each arm 101a. Each arm 101 a reciprocates in the direction of arrow ‘A’ in order todeliver a stile 120 to the assembly area where it is clamped to therails 110 a, 110 b by the clamps 180 a, 180 b, 180 c and 180 d. In orderto facilitate transfer of the assembled frame 150 from the clamps 180a-180 d to the conveyor 155, the conveyor 155 moves in the verticaldirection, designated by arrow ‘B’, toward the assembled frame 150suspended above the conveyor 155 so that the assembled frame 150 comesto rest on the conveyor 155 when released by the clamps 180 a-180 dwithout unwanted force of being dropped from the clamps 180 a-180 d ontothe conveyor 155. Alternatively, the assembled frame 150 may be movedvertically downward to come to rest on the conveyor 155.

In operation, the clamps 180 a-180 d release the assembled frame 150onto the conveyor 155 after a clamping period sufficient to permit theadhesive to cure sufficiently to maintain the connection between therails 110 and the stiles 120. The adhesive that secures the rails 110and the stiles 120 may be a thermoplastic hot melt that achieves anearly instantaneous bond. The adhesive is relatively viscous in orderto allow it to remain affixed to the rails 110 and the stiles 120without dripping. Unlike the adhesives securing the lock blocks 130 tothe stiles 120 and the core 140 to the rails 110, the adhesive securingthe rails 110 to the stiles 120 is relatively flexible and tacky,allowing the resulting frame 150 to be squared up as elsewhereexplained. The adhesive is applied to the rails 110 by being extrudedunder pressure through nozzles. Then, the clamps are moved to a positionadjacent the opposite ends of the rails 110 a, 110 b being delivered tothe jig 101 in preparation for assembling the next door frame.

It is noted that each clamp 180 a, 180 b, 180 c and 180 d shown in FIG.3 is provided with an adhesive extrusion system, including a reservoir,associated tubing connected to an extrusion nozzle, and a pump fortransporting the adhesive from the reservoir to the nozzle through thetubing, which includes one or more nozzles. When the clamps 180 a-180 dare positioned adjacent the opposite ends of the rails 110 a, 110 b, theclamps 180 a-180 d extrude an appropriate amount of adhesive onto theends of the rails 110 a, 110 b. The pressurized adhesive extrudate, forexample, is sent in the direction of arrows ‘C’ with respect to the rail110 a shown in FIG. 3 and in the similar direction with respect to therail 110 b. The adhesive is thus applied to exposed ends of the rails110, which are joined to edges at the ends of the stiles 120. While itis preferred to use extruded adhesive for fastening the corners of thestiles 120 and the rails 110 together, mechanical fasteners mayalternatively be used either separately or in conjunction with adhesive,such as applied through use of nail guns, corrugated fasteners and thelike. Yet alternatively, the stiles 120 and the rails 110 may beconnected through use of appropriately dimensioned and configured tongueand groove joints or other profiled joints sufficient to hold theresulting frame together for placement on a door skin, with the doorskin having an appropriately located adhesive to secure the door frameto the door skins.

After the adhesive is applied to the ends of the rails 110 a, 110 b, therespective stiles 120 are delivered from the arms 101 a to the assemblyarea where the stiles 120 are positioned adjacent the ends of the rails110 a, 110 b and clamped by the clamps 180 a, 180 b, 180 c and 180 d. Itwill be understood by those of skill in the art that the clamps 180a-180 d are designed for movement within the space defined by the jig101 between the clamping position shown in FIG. 3 to an extrusionposition adjacent the rails 110 a, 110 b. Additionally, the clamps 180a-180 d are provided with suitable extrusion mechanisms to accomplishthe foregoing extrusion operation.

With reference to FIGS. 1A and 1B, it is noted that the frame assemblyjig 101 supplies assembled frames 150 to the conveyor 155 for furtherprocessing by the door production line. In the preferred embodiment, asecond frame assembly station 100′ is provided that has the samefeatures and structures as the frame assembly station 100 describedabove. Like the frame assembly station 100, the second frame assemblystation 100′ uses automated technology to manufacture assembled doorframes 150′ which are the same as door frames 150 and these door frames150′ are delivered downstream via conveyor 155′ for further processingas described below. As best shown in FIG. 1A, the second frame assemblystation 100′ includes all of the same structure as the first frameassembly station 100. Like parts are labeled with like referencenumerals, except that the reference numerals of the second frameassembly station are indicated with a prime ′.

After each frame 150, 150′ is assembled, either through the assemblysystem and process described above or preassembly, the frame 150, 150′is moved to an adhesive coating station 210, 210′ and adhesive coatingand layup station 200. In the interest of brevity, only the first frame150 and first adhesive coating station 210 are discussed below. Theadhesive coating station 210 is capable of applying an adhesive to bothsides of the frame 150. Adhesive application may be accomplished bypassing the frame 150 through a double roll coater of the frame adhesivestation 210. In an exemplary embodiment, the roll coater appliesadhesive to the frame 150 in an amount between about 6 and about 25g/sft (grams per square foot) as measured on the surface of the stiles120 and the rails 110. In various exemplary embodiments, the amount ofadhesive is between about 15 and about 20 g/sft. This amount of adhesiveis believed to assist quality issues, such as by preventing pillowing orpeeling of the door skin from the frame 150. After the adhesive isapplied, the frame 150 is transferred to door skin assembly stage of theadhesive coating and layup station 200. The adhesive is preferably areactive hot melt adhesive or a polyurethane reactive (PUR) hot meltadhesive. The adhesive has an open time of about 90 seconds, sufficientto allow the door to be assembled, transported to the pressing station400 and thereafter pressed. The adhesive has an extended open time andhigh tack. Full cure of the adhesive typically takes 24 hours or more.If a PUR is used, the moisture needed for the reaction is available fromthe 6% to 8% moisture content of the door skins and the 6% to about 10%moisture content of the stiles/rails.

Referring to FIG. 1B, it will be understood that the frame assemblystations 100, 100′ deliver assembled frames 150, 150′ via conveyors 155,155′ which run parallel to each other. The frame adhesive coatingstation 210 will now be described and it will be understood by those ofskill in the art that a similar frame adhesive coating station 210′receives door frames 150′ in the same manner as described below withrespect to the frame 150. It should further be understood that third,fourth, fifth, and other production lines with corresponding stationsmay be provided.

The frame 150 is delivered to the frame adhesive coating station 210 viaconveyor 155. As the frame 150 passes through the frame adhesive coatingstation 210, adhesive is applied to both opposite sides of the frame150, while a first door skin 220 is delivered from the door skindelivery station 300 via conveyor 310 (See FIG. 1B). The door skin 220is delivered automatically to a bottom skin layup area 205 and locatedby positioning members within a bottom skin layup area 205 downstream offrame adhesive coating station 210. At the bottom skin layup area 205,the door skin 220 is located downstream of the frame adhesive coatingstation 210 and the frame 150 exiting the adhesive coating station 210is retrieved by robotic handling device 212 described below. The robotichandling device 212 (see FIG. 1B and FIGS. 4A-4C) is configured toretrieve the assembled frame 150 after application of adhesive, andthereafter place the assembled frame 150 onto the door skin 220 whichhas been located in the bottom skin layup area 205. After the assembledframe 150 has been placed onto the door skin 220, the frame/skinassembly is conveyed to a top skin layup area 215.

As shown in FIG. 1B and FIGS. 4A-4C robotic handling devices 212, 212′are utilized at bottom skin layup areas 205, 205′ to retrieve the doorframe 150, 150′ exiting the frame adhesive coating station 210, 210′. Inthe preferred embodiment, the robotic handling device 212 includes threesynchronized handling arms 213 a, 213 b, 213 c which retrieve theassembled frame 150 via gripping rollers as it exits the frame adhesivecoating station 210 and locate the frame 150 onto the respective bottomdoor skin 220. The three handling arms 213 a-213 c are synchronized suchthat two of the three arms 213 a-213 c (213 a and 213 c in FIG. 4A)place an assembled door frame 150 onto a bottom door skin 220 while thethird handling arm (213 b in FIG. 4A) begins to retrieve the next doorframe 150 from the adhesion station 210. FIG. 4C also shows an alignmentplate 215 for aligning with and squaring the door frame 150 prior to thedoor frame 150 being placed onto the bottom door skin 220, as will bedescribed in more detail below.

With reference to FIG. 4D, the handling arms 213 b, 213 c areschematically shown gripping the door frame 150. Each handling arm 213b, 213 c comprises gripping rollers 214 b, 214 c that grip oppositevertical surfaces of each stile 120 of the door frame 150. The grippingrollers 214 b, 214 c are rotatably mounted on the handling arms 213 b,213 c and reciprocate toward and away from the stiles 120 to perform thegripping action. During operation, two of the handling arms 213 b, 213 cselectively grip a door frame 150 exiting the adhesive coating station210 with the gripping rollers 214 b, 214 c and deliver the frame 150toward the bottom skin layup areas 205. Prior to placing the door frame150 onto the bottom skin 220, the handling arms 213 b, 213 c drive theforward rail 110 against the alignment plate 215 in order to square-upthe door frame 150 which may have shifted or become misaligned duringtransport along the conveyor 155 and through the adhesive coatingstation 210. More specifically, the door frame 150 is pushed against thealignment plate 215 and, if the door frame is not square (see dottedlines in FIG. 4D), the rail 110 will be pushed until it is flush againstthe alignment plate 215 to square the door frame 150. The grippingrollers 214 b, 214 c are adapted to rotate during the alignment process.In the preferred embodiment, the alignment plate 215 may be movedhorizontally into and out of the bottom skin layup areas 205 to contactthe door frame 150 and then move out of the layup area 205 duringplacement of the door frame 150 onto the bottom door skin 220. Thesecond production line (designated with primes ′) operates in the samemanner.

With reference to FIG. 1B, the door skin delivery station 300 provides asystem for delivering door skins 220 to the door assembly stage of theadhesive coating and layup station 200. More specifically, the door skindelivery station 300 includes an operator O2 who places by hand a seriesof door skins 220 onto conveyor 305 and a second operator O3 who placesby hand a series of door skins 230 onto conveyor 315. The door skins 220are conveyed to a flipper, preferably in the form of a star conveyor308, where the door skins 220 are flipped over so that their intendedouter surfaces rest on the conveyor and thereby expose the intendedinner surfaces of the door skins 220. An exemplary star conveyor 308 isshown in FIG. 8. The flipped door skins 220 are conveyed by conveyor 310to the bottom layup area 205 or 205′. The door skins 230 are conveyed byconveyor 315 to conveyor 320 without being flipped (so that theirinterior surfaces rest on the conveyor 320), and the door skins 230 arethen conveyed by the conveyor 320 to the top skin layup area 215 or215′.

As evident from FIG. 1B, the door skin assembly station 300 includes afirst skin feeder and a second skin feeder. The skin feeders may includea door skin pallet or multiple pallets of the door skins 220 and 230. Inthe exemplary embodiment, the first skin conveyor 310 provides bottomdoor skins 220 and the second skin feeder 320 provides top door skins230. The top and bottom door skins 220, 230 may be any variety of doorskins including wood composite door skins, solid wood door skins,polymer door skins, sheet molding compound door skins,fiberglass-reinforced skins, molded door skins, steel door skins, andflush door skins. Although two skin conveyors 310, 320 are shown, asingle skin conveyor may be utilized which provides both the top andbottom door skins 220, 230. Alternatively, additional conveyors may beprovided.

Door skins 220, 230 may be unloaded from the pallets P and placed ontothe conveyors 305, 315 either manually or through a robotic handlingdevice such as a vacuum gantry. If the door skins 220, 230 are removedfrom the pallets P manually, the operators O2, O3 moving the door skins220, 230 may also perform a visual quality inspection. If a door skin220, 230 is found to be unsatisfactory, the operator may place it on adisposal conveyor (not shown). If the door skin 220, 230 is found to beacceptable, the operator(s) O2, O3 places it on a production conveyor.Alternatively, the door skin 220, 230 may be removed from the pallets Pwith an automated device and a camera or set of cameras may be orientedand directed so that a remote operator can perform visual inspection.The operator O2, O3 is then able to determine if the door skins 220, 230are acceptable and signal the robotic handling system to place the doorskins 220, 230 on either the production conveyor or the disposalconveyor. In various exemplary embodiments, the inspection may beperformed automatically by tactile inspection devices, such as touchprobes, and/or non-tactile inspection devices, such as laser or opticalsensors. For example, a camera may optically capture the image of a doorskin 220, 230. The image may then be processed and measured by acontroller or microprocessor. If the door skin 220, 230 is acceptable,the controller/microprocessor can signal the robotic handling device toplace the door skin 220, 230 on the production conveyor 305, 315. If thedoor skin 220, 230 is not accepted, the controller/microprocessorsignals the robotic handling device to place the door skin 220, 230 onthe disposal conveyor.

Turning now to the top skin layup station, the top door skin 230 ismoved to the top door skin layup station 215 or 215′. At the top doorskin layup station 215 or 215′, the top door skin 230 is placed onto theframe 150 or 150′ opposite the bottom door skin 220 so that the interiorsurface of the top door skin 230 faces downwardly towards the frame 150or 150′. In the preferred embodiment, the top door skin 230 is liftedfrom conveyor 320 by a vacuum cup lifting structure, for example, asbest shown in FIGS. 5A-5C. As best depicted in FIG. 5A, the top doorskin is lifted from the conveyor 320 by an array ofpneumatically-actuated vacuum cups 330 mounted to a movable supportstructure 340. As best shown in FIG. 5B, the door skin 230 is positionedabove a respective door frame 150, 150′ placed on a bottom skin at layupstation 205, 205′. As best shown in FIG. 5C, the top door skin 230 isthen placed onto the frame 150, 150′. Various stops, limits, tactilesensors, and non-tactile sensors may be used to align and position thedoor skin 230 and the frame 150, 150′ so that the door frame is squaredprior to receiving the door skins 220, 230 at the layup stations 205,205′, 215, 215′.

Referring now only to the first assembly line in the interest ofbrevity, after the top door skin 230 is placed onto frame 150, theassembled door layup is transferred to a pressing station 400 where thedoor is pressed to more fixedly bond the door skins 220, 230 to theframe 150 having the core 140. As discussed above, because theproduction line is automated, each step is performed at the set rate ofmovement to avoid bottlenecks. For example, the amount of time for thelock block attachment station(s) 139 a, 139 b to attach the lock blocks130 to the stiles 120 is equal to rate of movement, the time for theframe 150 to be transferred to the adhesive coating and layup station200 equals the rate of movement, and the time in between completed doorscoming off the production line is equal to the rate of movement. Invarious exemplary embodiments, the rate of movement of the presentlydescribed system is about 7 seconds to about 15 seconds, for exampleabout every 8 seconds, though the time may vary depending on severalfactors such as the adhesive selected, as would be understood by one ofordinary skill in the art upon viewing this disclosure. The rate ofmovement may not be long enough, however, for sufficient bond strengthto form between the door skins 220, 230 and the frame 150.

As best shown in FIGS. 1B and 6A-6E, the double press 420 allows for apressing time that at least achieves the required throughput of pressingstation 400, 400′. Again in the interest of brevity, only pressingstation 400 is discussed below, with the understanding that pressingstation 400′ operates in a like manner. Although the pressing station400 is depicted with a double press 420, it should be understood thatthe pressing station 400 may include three, four, or more presses. Eachof the presses has a pair of spaced, movable platens operated by ahydraulic system. The double press 420 includes a lower press 420 a andan upper press 420 b. FIG. 6A depicts an assembled door layup (withframe 150 and door skin 230) entering the first press 420 a aligned withthe conveyor 155. The assembled door layup is passed to a conveyorlocated in the first press 420 a. In accordance with the preferredembodiment, the press thereafter is indexed down to align the secondpress 420 b with the conveyor 155. The press 420 reciprocates verticallyin response to its supporting hydraulic actuators in order to move thepresses 420 a, 420 b vertically in tandem with one another. The pressesare alternatingly moved between a loading/unloading position and apressing position. When either one of the presses 420 a, 420 b is in itsloading/unloading position, that press 420 a or 420 b is in operativealignment with the loading and discharging material handling andmovement devices, e.g., conveyor 155, to receive at least a firstassembled door layup delivered by the loading material handling andmovement device and to discharge at least a second assembled door thathas been pressed to the discharging material handling and movementdevice. The platens of the press 420 a or 420 b in the loading/unloadingposition are in an open state or mode to receive at least the firstassembled door layup and to discharge at least the pressed secondassembled door. At the same time, the other press 420 a or 420 b in thepressing position has its respective platens closed for pressing atleast a third assembled door layup. The press 420 a or 420 b in thepressing position is out of operative alignment with the loading anddischarging material handling and movement devices, e.g., conveyor 155.As shown in the drawings, in the “closed” state, the platens of thepress 420 a or 420 b do not necessary contact one another as they applypressure to the assembled door layup.

The alternating cycle of the press 420 assures that one press 420 a, 420b is pressing an already assembled door layup while the other press 420a, 420 b is either receiving an assembled door layup and/or dischargingan assembled door after having been pressed. FIG. 6C depicts thepressing station 400 wherein an assembled door layup is being receivedinto the top second press 420 b as shown in FIG. 6B. In FIG. 6D, thesecond (top) press 420 b is being closed to press the assembled doorlayup and the pressing station 400 is thereafter indexed to align the(lower) first press 420 a with the conveyor 155 as shown in FIG. 6A.Using the double press 420, the pressing of assembled door layups isalternated between the lower and upper presses 420 a, 420 b, with theresult that an assembled and fixed door exits each press 420 a, 420 bafter having been pressed for a period sufficient to bond the skins 220,230 to the frame 150. An assembled door layup can therefore undergo apressing operation, which may include opening and closing the platens ofthe lower and upper presses 420 a, 420 b, for approximately twice aslong as the rate of movement. The extra press time allows a greater bondto be created between the door skins 220, 230, and the frame 150 and thecore 140.

In various exemplary embodiments, the press imparts approximately 100psi to the door skins 220, 230 adjacent the stile and rail sections. Theprincipal bonding of the skins 220, 230 occurs along the stiles 120 andthe rails 110, the areas where the maximum pressure is applied. Thepressure along the remaining areas of the door skins 220, 230 coveringthe core 140 varies.

The double press 420 is capable of rapid closure. For example, an upperplaten and a lower platen in each of the lower and upper presses 420 a,420 b of the double press 420 are capable of transitioning from an openposition to a closed state of contacting the door skins 220, 230 andreaching a final pressure in fewer than 10 seconds. In various exemplaryembodiments, the double press 420 is capable of reaching final pressurein approximately one second or less. A fast closing double press 420allows for a faster acting adhesive to be used and therefore quicker setand cure times.

In various exemplary embodiments, one of the upper and lower platens orboth platens may be moved towards or away from the assembled door layup.As best shown in FIGS. 6C and 6D, actuators, such as hydraulic orpneumatic cylinders, may be connected to the upper platen. FIG. 6Edepicts an assembled and pressed door (frame 150 and top skin 230)leaving the lower first press 420 a and passing onto the dischargeconveyor. FIGS. 6B and 6C depicts the upper press 420 b in an openposition and the lower press 420 a in a closed position. Each of theupper and lower press 420 a, 420 b may also include a conveyor 465, forexample a belt conveyor or powered rollers as shown in FIG. 6A, toassist in loading and discharging the assembled and pressed door intoand from the respective presses 420 a, 420 b. In FIGS. 6A, 6B, and 6E,the lower platens are hidden by the conveyors 465. The conveyors 465remain within the respective presses 420 a, 420 b during pressingoperation. The conveyors 465 are preferably made from a flexiblematerial that is durable enough to withstand the pressure applied by theplatens. In various exemplary embodiments, the conveyor 465 may includea first side and a second side with an open center section (not shown).The first and second sides may include belts or rollers and bepositioned along the edges of the resulting door to contact the doorskins 220, 230 adjacent the frame 150. The first and second sideconveyors and open center section allow the lower platen to contact thecentral region of the bottom door skin 220 directly. Various otherdevices and methods allow for positioning the assembled door layups intothe lower and upper presses 420 a, 420 b, for example a push rod, mayalso be used. The double press 420 may also include various stops,limits, tactile sensors, and non-tactile sensors may be used to alignand position the door to square the frame 150 before pressing.

FIGS. 6F and 6G illustrate a schematic representation of the doublepress 420 in an upper position where the assembled door layup isdelivered into the upper press 420 b (FIG. 6F) and in a lower positionwhere the assembled door layup is delivered into the lower press 420 a(FIG. 6G). Movement of the entire press 420 between the upper position(FIG. 6F) and the lower position (FIG. 6G) is accomplished by hydrauliccylinder and piston assemblies 430. The lower press 420 a includes anupper/top platen 421 a and a lower/bottom platen 422 a, and the upperpress 420 b includes an upper/top platen 421 b and a lower/bottom platen422 b. Movement of the platens 421 a, 422 a of the first lower press 420a is accomplished by hydraulic cylinder and piston assemblies 440interconnecting the lower platen 422 a and the upper platen 421 a.Movement of the platens 421 b, 422 b of the second upper press 420 b isaccomplished by hydraulic cylinder and piston assemblies 450interconnecting the lower platen 422 b and the upper platen 421 b. Aswill be understood by one of skill in the art, the various hydrauliccylinder and piston assemblies may be driven by the hydraulic linesillustrated in FIGS. 6F and 6G.

As best shown in FIG. 1B, after leaving the pressing station 400, 400′(FIG. 1B), the assembled and pressed doors are then passed to anaccumulator station 500, 500′ preferably in the form of a non-linearaccumulator 520, 520′ that holds the assembled and pressed doors duringa cooling and curing period. The accumulator 520, 520′ thus reduces thefootprint of the production line while the doors are curing before beingsent for finishing as described below. FIG. 7 depicts a pair ofnon-linear accumulators 520, 520′ in the form of star conveyors whichreceive the assembled and pressed doors from conveyors 155, 155′,respectively, and rotate the assembled and pressed doors about an axisuntil the doors are discharged onto the single finishing conveyor 600(FIGS. 1B and 1C). As best shown in FIG. 1B, these side-by-sideaccumulators 520, 520′ transfer the doors assembled on parallel lines155, 155′ and pass through parallel presses 400, 400′ onto a singleconveyor 600. FIG. 8 depicts an exemplary motor driven, rotating starconveyor that has aligned and spaced cooperating arms that hold presseddoors of the type used as accumulators 520, 520′.

Although the exemplary embodiments discussed above are with respect to adouble press 420, it should be understood that the pressing apparatusmay alternatively have three, four, five, or more presses. As the numberof presses increases, the pressing time per press can likewise increasewithout slowing the overall movement time. Moreover, the presses 420 a,420 b may be placed side-by-side on the same level or otherwise orientedas opposed to the stacked relationship shown in FIGS. 6C and 6D. Variousmaterial handling devices, such as a switching conveyor, may provide theassembled door layups to the presses 420 a, 420 b, etc. in analternating or successive fashion.

As best shown in FIG. 1C, after transiting the pressing stations 400,400′ and the accumulators 500, 500′, the pressed assembled doors aremoved along conveyor 600 to a number of optional finishing stations asneeded. For example, a door may be passed through a stile trimmingstation 620 and a rail trimming station 640 to remove excess framematerial. If the blades of the trimming stations 620, 640 are notparallel the door may need to be rotated between the stile trimmingstation 620 and the rail trimming station 640. After the edges have beentrimmed, the door may be placed through an edge coating station 660 thatapplies a protective preferably colored coating to the exposed edges ofthe stiles. Because the stiles extend vertically in the assembled door,their edges are viewable to the user so the coating masks the edges andalso provides a protective barrier. Here the edges of the door, such asthe exposed rails 110 a, 110 b and stiles 120 may be coated, painted,laminated, or otherwise finished. Other painting or coating may beaccomplished at this station or separately.

When a door has completed assembly and pressing, it passes to aninspection station 670 and is inspected by an inspector I who checks thedoor for quality. In various exemplary embodiments the qualityinspection may be performed automatically as discussed above withrespect to the door skin delivery station 300. Any unacceptable door iseither discarded or reworked, and all doors passing inspection are sentto a star conveyor 680 and then to palletizer 690 for stacking.

A number of commonly used and commercially available adhesives have beendiscussed above such as PUR and EVA hot melt adhesives. However, aspectsof the present invention are also directed to the novel use of adhesivecompositions. In an exemplary embodiment, a PUR adhesive comprisingpolyurethane and isocyanurate is used in the above-disclosed system.These chemicals increase the initial green or set strength of theadhesives, securing the bond between the door skin and the frame,eliminating delamination caused by the stresses of bowed or warpedskins.

The foregoing detailed description of the certain exemplary embodimentshas been provided for the purpose of explaining the principles of theinvention and its practical application, thereby enabling others skilledin the art to understand the invention for various embodiments and withvarious modifications as are suited to the particular use contemplated.This description is not necessarily intended to be exhaustive or tolimit the invention to the precise embodiments disclosed. Additionalembodiments are possible and are intended to be encompassed within thisspecification and the scope of the appended claims. The specificationdescribes specific examples to accomplish a more general goal that maybe accomplished in another way.

What is claimed is:
 1. A system for making doors, comprising: a firstpressing station comprising a first press including a first set ofplatens, and a second press including a second set of platens, each setof platens respectively having at least one platen movable relative tothe other platen of the set of platens between an open state and aclosed state; a first loading device configured to deliver assembleddoors to the first pressing station; a first discharging deviceconfigured to receive the assembled doors that have been pressed by thefirst pressing station, the first pressing station configured toalternatingly move the first and second presses between (i) aloading/unloading position, in which one of the first and second pressesis in the open state and operative alignment with the first loading anddischarging devices to receive at least a first of the assembled doorsdelivered by the first loading device and to discharge at least a secondof the assembled doors that has been pressed to the first dischargingdevice, and (ii) a pressing position, in which the other of the firstand second presses is in the closed state for pressing a third of theassembled doors and is out of operative alignment with the first loadingand discharging devices; a first accumulator configured to hold theassembled doors that have been pressed in the first pressing stationwhile an applied adhesive develops bond strength; a second pressingstation comprising a third press including a third set of platens, and afourth press including a fourth set of platens, each set of platensrespectively having at least one platen movable relative to the otherplaten of the set of platens between an open state and a closed state; asecond loading device configured to deliver assembled doors to thesecond pressing station; a second discharging device configured toreceive the assembled doors that have been pressed by the secondpressing station, the second pressing station configured toalternatingly move the third and fourth presses between (i) aloading/unloading position, in which one of the third and fourth pressesis in the open state and operative alignment with the second loading andsecond discharging devices to receive at least a fourth of the assembleddoors delivered by the second loading device and to discharge at least afifth of the assembled doors that has been pressed to the seconddischarging device, and (ii) a pressing position, in which the other ofthe third and fourth presses is in the closed state for pressing a sixthof the assembled doors and is out of operative alignment with the secondloading and discharging devices; a second accumulator configured to holdthe assembled doors that have been pressed in the second pressingstation while an applied adhesive develops bond strength; and a singleconveyor configured to carry doors away from the first and secondaccumulators.
 2. The system of claim 1, wherein the first and secondpresses are movable vertically between the loading/unloading positionand the pressing position, and the third and fourth presses are movablevertically between the loading/unloading position and the pressingposition.
 3. The system of claim 1, further comprising hydraulics formoving the first and second presses vertically between theloading/unloading position and the pressing position, and for moving thethird and fourth presses vertically between the loading/unloadingposition and the pressing position.
 4. The system of claim 1, whereinthe first pressing station is configured to alternatively move the firstand second presses after each individual assembled door is delivered bythe first loading device, and wherein the second pressing station isconfigured to alternatively move the third and fourth presses after eachindividual assembled door is delivered by the second loading device. 5.The system of claim 1, wherein each of the first and second loadingdevices and the first and second discharging devices comprises aconveyor.
 6. The system of claim 1, wherein each of the first and secondaccumulators comprises a star conveyor.
 7. The system of claim 1,further comprising: a first frame assembly station configured to applyadhesive to door frame components and to frame the door frame componentsand applied adhesive into door frames; a first door assembly stationconfigured to secure door skins on opposites surfaces of the door framesassembled in the first frame assembly station to provide assembled doorsto be delivered to the first loading device; a second frame assemblystation configured to apply adhesive to door frame components and toframe the door frame components and applied adhesive into door frames;and a second door assembly station configured to secure door skins onopposites surfaces of the door frames assembled in the second frameassembly station to provide assembled doors to be delivered to thesecond loading device.
 8. The system of claim 7, wherein the first andsecond presses are movable vertically between the loading/unloadingposition and the pressing position, and the third and fourth presses aremovable vertically between the loading/unloading position and thepressing position.
 9. The system of claim 7, further comprisinghydraulics for moving the first and second presses vertically betweenthe loading/unloading position and the pressing position, and for movingthe third and fourth presses vertically between the loading/unloadingposition and the pressing position.
 10. The system of claim 7, whereinthe first pressing station is configured to alternatively move the firstand second presses after each individual assembled door is delivered bythe first loading device, and wherein the second pressing station isconfigured to alternatively move the third and fourth presses after eachindividual assembled door is delivered by the second loading device. 11.The system of claim 7, wherein each of the first and second loadingdevices and the first and second discharging devices comprises aconveyor.
 12. The system of claim 7, wherein each of the first andsecond frame assembly stations contains rail grippers configured tograsp rails of the frame components and to draw the rails apart from oneanother.
 13. The system of claim 1, further comprising a first conveyorfor transporting the assembled doors from the first pressing station tothe first accumulator, and a second conveyor for transporting theassembled doors from the second pressing station to the secondaccumulator.
 14. The system of claim 1, wherein the first conveyor andsecond conveyor are parallel to the single conveyor.